The doctors and nurses did best to fight Zika Virus(寨卡病毒) in Brazil.

The little boy took the back way quietly and quickly to escape________.[ ]

Let’s go to the concert tonight, Michael!—Sorry, I _______. I have to help my mother with the housework

The top student failed again in the examination and only then ______ the importance of reading and memorizing the English texts.

ought he couldn’t go to the party because he had to write a report, but he went ___________.